1) Field of the Invention
The present invention relates to a method for production of a conjugated diolefin by a fluidized bed reaction system using an oxide catalyst.
2) Description of Related Art
A method for subjecting monoolefins having four or more carbon atoms such as n-butene and isopentene and molecular oxygen to catalytic oxidative dehydrogenation to produce conjugated diolefins corresponding to these monoolefins such as 1,3-butadiene and isoprene, respectively, is well known, and many catalysts used for the oxidative dehydrogenation are proposed.
An important reaction in the chemical industry is a heterogeneous reaction in which two phases such as gas-solid are involved, and ammonia synthesis, ethylene oxide synthesis, catalytic cracking of oil, and the like are known as heterogeneous reactions in which oxide catalysts are industrially used.
A reaction system in which an oxide catalyst is used includes a fixed bed, a fluidized bed, and a moving bed. Among these, a fixed bed reaction system is frequently industrially employed utilizing the advantage that the fluid state of gas is close to an extruding flow and the reaction yield can be increased. However, the fixed bed reaction system has a low heat transfer performance and is unsuitable for an exothermic reaction and an endothermic reaction requiring cooling and heating, respectively. Particularly, in an intense exothermal reaction like oxidation reaction, there is a problem that the temperature rapidly rises to a state where it is difficult to be controlled and there is a possibility that a reaction may proceed extremely may be initiated. There is also a problem that a catalyst will suffer damage and will deteriorate at an early stage by such a rapid temperature rise.
On the other hand, the fluidized bed reaction system, in which catalyst particles are moving rapidly in the reactor, has advantages that (1) it has a high heat transfer performance, can maintain the temperature in the reactor at a substantially constant level even during a highly exothermic or endothermic reaction, and can suppress excessive reaction progress; and (2) since local accumulation of energy is suppressed, a raw material gas within the range of explosion can be reacted safely, and so it is possible to increase the raw material concentration to improve productivity. Therefore, the fluidized bed reaction system is suitable for the oxidative dehydrogenation of hydrocarbons which is a strong exothermic reaction. For example, the oxidative dehydrogenation to synthesize 1,3-butadiene from butene is an exothermic reaction of about 30 kcal/mol.
Although advantageous points of the fluidized bed reaction system as described above are known, Patent Documents 1 and 2, for example, describe that when unsaturated hydrocarbons are generally converted to unsaturated aldehydes or diolefins, the use of a fixed bed catalyst is preferred. Further, Patent Document 3 describes that in the production of conjugated dienes by the oxidative dehydrogenation of monoolefins, the catalyst described in the Patent Document can be used in all the methods of a fixed bed, a moving bed, and a fluidized bed, but there is no specific description in it about reaction systems other than a fixed bed.    [Patent Document 1] Japanese Patent Publication No. 49-14392    [Patent Document 2] Japanese Patent Publication No. 61-12488    [Patent Document 3] Japanese Patent Publication No. 03-16929